Run Expectancy

Run expectancy is the average number of runs a team is expected to score from a given base/out situation through the end of the inning. It is derived from historical play-by-play data and represents what happens on average across thousands of similar situations.

The 24 Base/Out States

Baseball has 24 possible combinations of base runners and outs:

• 3 out states (0, 1, or 2 outs)
• 8 base configurations (empty, first only, second only, third only, first and second, first and third, second and third, bases loaded)

The run expectancy matrix assigns a number to each of these 24 states. Here are approximate MLB values:

Situation	0 Outs	1 Out	2 Outs
Bases empty	0.48	0.25	0.10
Runner on 1st	0.87	0.51	0.22
Runner on 2nd	1.10	0.66	0.31
Runners on 1st & 2nd	1.47	0.90	0.43
Bases loaded	2.28	1.55	0.76

(Values are approximate and vary by era and league.)

How Coaches Use It

Run expectancy is most useful for evaluating whether tactical decisions, bunting, stealing, hitting and running, actually improve scoring chances.

Sacrifice bunt example: With a runner on first and nobody out (RE: ~0.87), a successful sacrifice bunt produces a runner on second with one out (RE: ~0.66). The sacrifice bunt reduced expected runs by about 0.21. This does not mean bunting is always wrong, late in a close game, trading run expectancy for increased probability of scoring exactly one run can be rational, but it explains why analysts are skeptical of routine first-inning sacrifices.

Stolen base example: The value of a stolen base must exceed the cost of a caught stealing. Getting caught eliminates the runner and costs an out. Whether the risk is worth it depends on the probability of success and the run expectancy change.

At the Youth Level

Youth coaches do not need to memorize the matrix. The underlying principle is useful: outs are precious. Every out costs your team something. Giving away outs with bunts, risky steals, or aggressive baserunning decisions has a real cost, even when it does not feel like it. Teaching players to treat outs like currency, and to understand that giving an out "for a base" is not automatically a good trade, is the practical takeaway.